Brushless Motor Circuit Board Integration for Handheld Grinder

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Solution Overview

Problem

Handheld power tools with brushless electric motors face issues of increased volume, heat generation, and reliability due to multiple circuit boards and connections that are prone to wear and breakage, leading to a need for a more compact, cooler, and reliable design.

Innovation Solution

A handheld power tool with a single circuit board that integrates a rectifier, DC bus capacitors, an integrated power module, and a power switch, minimizing inter-board connections and using smaller, film capacitors and heat sinks to reduce size and heat generation, while maintaining reliability and efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple circuit boards are used to support capacitor, power switch and control circuitry, then the power tool can perform required functions, but the volume of the power tool increases and connections become susceptible to wearing out or breaking

Engineering Contradiction:

ImprovereliabilityVSAvoidvolume

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

The patent consolidates multiple circuit boards into a single circuit board that integrates the capacitor, power switch, and control circuitry. This merging eliminates inter-board connections, reducing volume while improving reliability by removing potential failure points from connection wear and breakage.

Inventive Principle:

Principle #5Merging (Combining)

2Reliability

If capacitor and power switch are used to control current flow and provide current when AC input voltage is unable to do so, then the brushless electric motor can operate reliably, but undesirable heat is generated

Engineering Contradiction:

ImprovereliabilityVSAvoidheat generation

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent positions the heat-generating components (capacitor and power switch) directly on the circuit board that is mounted to the housing, utilizing the housing as a heat sink. This converts the harmful heat generation into a manageable thermal situation by providing direct thermal conduction path to the housing, which acts as a heat dissipation structure.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Adaptability or versatility

If multiple circuit boards with inter-board connections are used, then the power tool can support all required components, but the connections are susceptible to wearing out or breaking

Engineering Contradiction:

Improvecomponent support capabilityVSAvoidconnection reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent integrates all required components (rectifier, DC bus capacitors, integrated power module with motor switches, and control circuitry) onto a single circuit board. This eliminates all inter-board connections, removing the reliability issue of connection wear and breakage while maintaining full component support capability through careful circuit board layout and integration.

Inventive Principle:

Principle #5Merging (Combining)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution results in a more compact, reliable, and efficient power tool with reduced heat generation and fewer inter-board connections, enhancing its operational stability and user experience.

Implementation Method 1

Power tools with brushless electric motors use a rectifier to convert an alternating current (AC) input into a direct current (DC) that is used to drive the brushless electric motor.

Methodology Applied

Scientific EffectRectification:

Implementation Method 2

Power tools with brushless electric motors also employ a capacitor to lessen ripple and to provide a current when the AC input voltage is unable to do so.

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 3

The capacitor and the power switch generate undesirable heat

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 4

using smaller, film capacitors and heat sinks to reduce size and heat generation

Methodology Applied

Scientific EffectHeat dissipation: Heat Sink

Data Source

PatentEP2873494B1A handheld grinder with a brushless electric motor

Publication Date: 2017.11.22 BLACK & DECKER CORP

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AI summary

A handheld grinder (10) comprising a housing (12); a grinding disk (22); a motor (28); an output shaft connected to the grinding disk (22) and the motor (28) to impart rotary motion thereto; and a circuit board (40) residing in the housing (12) and having thereon a rectifier (44) that receives an alternating current and converts the alternating current to a direct current, a switching arrangement having a plurality of motor switches connected electrically between the rectifier (44) and the motor (28) and operates to deliver the direct current from the rectifier (44) to the motor (28), a capacitor (50) connected electrically between the rectifier (44) and the switching arrangement, wherein the capacitor (50) is coupled in parallel across the rectifier (44), a driver circuit interfaced with the motor switches and operable to control switching operation of the motor switches, and a power switch (32) connected electrically between the rectifier (44) and the driver circuit and operable to selectively energize the driver circuit and power on the grinder disk (22).